1. Field
The following description relates to a driving technique of a trigger circuit. The following description also relates to such a trigger circuit and a light apparatus having such a trigger circuit that are capable of controlling a turn-off time of a driving switching element to provide a boundary conduction mode.
2. Description of Related Art
A power factor correction converter generally operates in a continuous conduction mode and in a boundary conduction mode. The continuous conduction mode may use a fixed frequency of an integrated circuit (IC) to control an inductor current or a driving current. The boundary conduction mode may use a variable frequency to turn on a driving switch when the inductor current reaches a zero value.
A Light Emitting Diode (LED) light apparatus may be driven through a switching converter method. Also, a switching converter may be classified according to a Buck-type, a Boost-type and a Buck-Boost-type. A Buck-type converter is a DC-to-DC power converter which steps down voltage while stepping up current from its input to its output. A Boost-type converter is a DC-to-DC power converter which steps up voltage while stepping down current from its input to its output. A Buck-Boost-type converter is a converter that is able to operate as either a Buck-type converter or a Boost-type converter. Previously, the switching converter of the Boost-type was most commonly used, but more recently the Buck-type is used more commonly for a cost reduction of the integrated circuit (IC). In general, a type of the switching converter may be classified according to a ratio of an input voltage and an output voltage, as discussed, and may include a MOSFET in order to provide an average inductor current mode method.
An existing technology may use a drain voltage of the MOSFET for detecting a time point at which the inductor current reaches the zero value. The drain voltage of the MOSFET may rapidly decrease at the time point when the inductor current reaches the zero value, so the integrated circuit (IC) may use an external high breakdown voltage element for detecting the time point when the inductor current reaches the zero value. However, the existing technology uses the high breakdown voltage element, which causes a price competitiveness problem.